Interference fits are often employed to hold two axially aligned components (such as shafts, bushings, bearings etc.) with respect to each other. Simply put, an interference fit is achieved when the outer cylindrical surface of a first component is forced into the inner cylindrical surface of a second component such that the diameter of the outer cylindrical surface of the first component is larger than the diameter of the inner cylindrical surface of the second component. By this arrangement, the components mutually exert radial pressure and effectively hold each other in position.
It can be appreciated that interference fits are possible if mating surfaces belonging to both interacting components are manufactured to tight geometric tolerances. If one component is manufactured via a process that is not capable of maintaining tight tolerances, then the other component would not properly assemble despite the tightness of its tolerance. Consequently, an interference fit would not be possible to hold the two components in place.
Furthermore, it can be appreciated that when the geometry of the two mating components is such that the two mating surfaces need to traverse mutually across a considerable distance till the first component is positioned appropriately with respect to the second a traditional interference fit has other inherent problems. Such problems include but are not limited to encountering excessive assembly forces, damaging either one or both of the mating components, and the general inability to properly control the final seating location of the first component with respect to the second component.